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  • Using "public" vars or attributes in class calls, functional approach

    - by marw
    I was always wondering about two things I tend to do in my little projects. Sometimes I will have this design: class FooClass ... self.foo = "it's a bar" self._do_some_stuff(self) def _do_some_stuff(self): print(self.foo) And sometimes this one: class FooClass2 ... self.do_some_stuff(foo="it's a bar") def do_some_stuff(self, foo): print(foo) Although I roughly understand the differences between functional and class approaches, I struggle with the design. For example, in FooClass the self.foo is always accessible as an attribute. If there are numerous calls to it, is that faster than making foo a local variable that is passed from method to method (like in FooClass2)? What happens in memory in both cases? If FooClass2 is preferred (ie. I don't need to access foo) and other attributes inside do not change their states (the class is executed once only and returns the result), should the code then be written as a series of functions in a module?

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  • Abstract base class puzzle

    - by 0x80
    In my class design I ran into the following problem: class MyData { int foo; }; class AbstraktA { public: virtual void A() = 0; }; class AbstraktB : public AbstraktA { public: virtual void B() = 0; }; template<class T> class ImplA : public AbstraktA { public: void A(){ cout << "ImplA A()"; } }; class ImplB : public ImplA<MyData>, public AbstraktB { public: void B(){ cout << "ImplB B()"; } }; void TestAbstrakt() { AbstraktB *b = (AbstraktB *) new ImplB; b->A(); b->B(); }; The problem with the code above is that the compiler will complain that AbstraktA::A() is not defined. Interface A is shared by multiple objects. But the implementation of A is dependent on the template argument. Interface B is the seen by the outside world, and needs to be abstrakt. The reason I would like this is that it would allow me to define object C like this: Define the interface C inheriting from abstrakt A. Define the implementation of C using a different datatype for template A. I hope I'm clear. Is there any way to do this, or do I need to rethink my design?

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  • Nested class or not nested class?

    - by eriks
    I have class A and list of A objects. A has a function f that should be executed every X seconds (for the first instance every 1 second, for the seconds instance every 5 seconds, etc.). I have a scheduler class that is responsible to execute the functions at the correct time. What i thought to do is to create a new class, ATime, that will hold ptr to A instance and the time A::f should be executed. The scheduler will hold a min priority queue of Atime. Do you think it is the correct implementation? Should ATime be a nested class of the scheduler?

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  • C++ threaded class design from non-threaded class

    - by macs
    I'm working on a library doing audio encoding/decoding. The encoder shall be able to use multiple cores (i.e. multiple threads, using boost library), if available. What i have right now is a class that performs all encoding-relevant operations. The next step i want to take is to make that class threaded. So i'm wondering how to do this. I thought about writing a thread-class, creating n threads for n cores and then calling the encoder with the appropriate arguments. But maybe this is an overkill and there is no need for another class, so i'm going to make use of the "user interface" for thread-creation. I hope there are any suggestions.

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  • Include a Class in another model / class / lib

    - by jaycode
    I need to use function "image_path" in my lib class. I tried this (and couple of other variations): class CustomHelpers::Base include ActionView::Helpers::AssetTagHelper def self.image_url(source) abs_path = image_path(source) unless abs_path =~ /^http/ abs_path = "#{request.protocol}#{request.host_with_port}#{abs_path}" end abs_path end end But it didn't work. Am I doing it right? Another question is, how do I find the right class to include? For example if I look at this module: http://api.rubyonrails.org/classes/ActionView/Helpers/AssetTagHelper.html is there a rule of thumb how to include that module in a model / library / class / anything else ?

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  • How to call a method from another class that's been instantiated within the current class

    - by Pavan
    my screen has a few views like such __________________ | _____ | | | | | //viewX is a video screen | | | | | viewX | vY | | //viewY is a custom uiview i created. | |____| | //it contains a method which i would like to call that toggles |_________________| //the hidden property of this view. and when it hides, a little | | //button is replaced no the top right corner on top of viewX | viewZ | //the video layer | | |_________________| //viewZ is a view containing many square views - thumbnails. my question is, i dont know how to register for touch events so that it recognises any touch event on no matter which view the user touches the screen.. atm im handling the touch events for each view inside it. so all works well... however what im trying to do is that when the user taps anywhere else on the screen but on viewY, viewY should dissapear by calling that method in the viewY class. this viewY class is instantiated and has no xib file attached to it. the uiview is created progammatically in the viewY class. this whole class for viewY behviour is instantiated in viewX - the video view. my boss says add delegates.. although i have now clue how to do that... any help? is there anyway i can just make it really simple and be able to say REMOVE VIEW no matter which class im calling from? Also ive seen other people achieve this by using these funky arrows - ... <- etc.. although im not sure if thats what i need or how to implement such a thing. ah i think ive made my question quite complicated but i really mean it to be a simple one, and know it can be done in an easy way!

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  • Use nested static class as ActionListener for the Outer class

    - by Digvijay Yadav
    I want to use an nested static class as an actionListener for the enclosing class's GUI elements. I did something like this: public class OuterClass { public static void myImplementation() { OuterClass.StartupHandler startupHandler = new OuterClass.StartupHandler(); exitMenuItem.addActionListener(startupHandler); // error Line } public static class StartupHandler implements ActionListener { @Override public void actionPerformed(ActionEvent e) { //throw new UnsupportedOperationException("Not supported yet."); if (e.getSource() == exitMenuItem) { System.exit(1); } else if (e.getSource() == helpMenuItem) { // show help menu } } } } But when I invoke this code I get the NullPointerException at the //error Line. Is this the right method to do do this or there is something I did am missing?

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  • Thread class closing from other Class (Activity) with protected void onStop() Android

    - by user1761337
    I have a Problem with Closing the Thread. I will Closing the Thread with onStop,onPause and onDestroy. This is my Source in the Activity Class: @Override protected void onStop(){ super.onStop(); finish(); } @Override protected void onPause() { super.onPause(); finish(); } @Override public void onDestroy() { this.mWakeLock.release(); super.onDestroy(); } And the Thread Class: public class GameThread extends Thread { private SurfaceHolder mSurfaceHolder; private Handler mHandler; private Context mContext; private Paint mLinePaint; private Paint blackPaint; //for consistent rendering private long sleepTime; //amount of time to sleep for (in milliseconds) private long delay=1000/30; //state of game (Running or Paused). int state = 1; public final static int RUNNING = 1; public final static int PAUSED = 2; public final static int STOPED = 3; GameSurface gEngine; public GameThread(SurfaceHolder surfaceHolder, Context context, Handler handler,GameSurface gEngineS){ //data about the screen mSurfaceHolder = surfaceHolder; mHandler = handler; mContext = context; gEngine=gEngineS; } //This is the most important part of the code. It is invoked when the call to start() is //made from the SurfaceView class. It loops continuously until the game is finished or //the application is suspended. private long beforeTime; @Override public void run() { //UPDATE while (state==RUNNING) { Log.d("State","Thread is runnig"); //time before update beforeTime = System.nanoTime(); //This is where we update the game engine gEngine.Update(); //DRAW Canvas c = null; try { //lock canvas so nothing else can use it c = mSurfaceHolder.lockCanvas(null); synchronized (mSurfaceHolder) { //clear the screen with the black painter. //reset the canvas c.drawColor(Color.BLACK); //This is where we draw the game engine. gEngine.doDraw(c); } } finally { // do this in a finally so that if an exception is thrown // during the above, we don't leave the Surface in an // inconsistent state if (c != null) { mSurfaceHolder.unlockCanvasAndPost(c); } } this.sleepTime = delay-((System.nanoTime()-beforeTime)/1000000L); try { //actual sleep code if(sleepTime>0){ this.sleep(sleepTime); } } catch (InterruptedException ex) { Logger.getLogger(GameThread.class.getName()).log(Level.SEVERE, null, ex); } while (state==PAUSED){ Log.d("State","Thread is pausing"); try { this.sleep(1000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } } }} How i can close the Thread from Activity Class??

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  • Django: Inherit Permssions from abstract models?

    - by lazerscience
    Is it possible to inherit permissions from an abstract model in Django? I can not really find anything about that. For me this doesn't work! class PublishBase(models.Model): class Meta: abstract = True get_latest_by = 'created' permissions = (('change_foreign_items', "Can change other user's items"),) EDIT: Not working means it fails silently. Permission is not created, as it wouldn't exist on the models inheriting from this class.

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  • C#: Abstract classes need to implement interfaces?

    - by bguiz
    My test code in C#: namespace DSnA { public abstract class Test : IComparable { } } Results in the following compiler error: error CS0535: 'DSnA.Test' does not implement interface member 'System.IComparable.CompareTo(object)' Since the class Test is an abstract class, why does the compiler require it to implement the interface? Shouldn't this requirement only be compulsory for concrete classes?

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  • What is the purpose of abstract classes?

    - by SpikETidE
    I am trying to learn OOP in PHP, and I have some confusion about interfaces and abstract classes. They both contain no implementations, only definitions, and should be implemented through their sub-classes. What part of abstract classes clearly distinguishes them from interfaces? Also, due to their apparent similarities, based on what reasons should I decide to use one over the other?

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  • Abstract attributes in Python

    - by deamon
    What is the shortest / most elegant way to implement the following Scala code with an abstract attribute in Python? abstract class Controller { val path: String } A subclass of Controller is enforced to define "path" by the Scala compiler. A subclass would look like this: class MyController extends Controller { override val path = "/home" }

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  • Single Table Per Class Hierarchy with an abstract superclass using Hibernate Annotations

    - by Andy Hull
    I have a simple class hierarchy, similar to the following: @Entity @Table(name="animal") @Inheritance(strategy=InheritanceType.SINGLE_TABLE) @DiscriminatorColumn(name="animal_type", discriminatorType=DiscriminatorType.STRING) public abstract class Animal { } @Entity @DiscriminatorValue("cat") public class Cat extends Animal { } @Entity @DiscriminatorValue("dog") public class Dog extends Animal { } When I query "from Animal" I get this exception: "org.hibernate.InstantiationException: Cannot instantiate abstract class or interface: Animal" If I make Animal concrete, and add a dummy discriminator... such as @DiscriminatorValue("animal")... my query returns my cats and dogs as instances of Animals. I remember this being trivial with HBM based mappings but I think I'm missing something when using annotations. Can anyone help? Thanks!

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  • can this keyword be used in an abstract class in java

    - by Reddy
    I tried with below example, it is working fine. I expected it to pick sub-class's value since object won't be created for super class (as it is abstract). But it is picking up super class's field value only. Please help me understand what is the concepts behind this? abstract class SuperAbstract { private int a=2; public void funA() { System.out.println("In SuperAbstract: this.a "+a); } } class SubClass extends SuperAbstract { private int a=34; } I am calling new SubClass.funA(); I am expecting it to print 34, but it is printing 2.

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  • can the keyword 'this' be used in an abstract class in java

    - by Reddy
    I tried with below example, it is working fine. I expected it to pick sub-class's value since object won't be created for super class (as it is abstract). But it is picking up super class's field value only. Please help me understand what is the concepts behind this? abstract class SuperAbstract { private int a=2; public void funA() { System.out.println("In SuperAbstract: this.a "+a); } } class SubClass extends SuperAbstract { private int a=34; } I am calling new SubClass.funA(); I am expecting it to print 34, but it is printing 2.

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  • Using Lazy<T> and abstract wrapper class to lazy-load complex system parameters

    - by DigiMortal
    .NET Framework 4.0 introduced new class called Lazy<T> and I wrote blog post about it: .Net Framework 4.0: Using System.Lazy<T>. One thing is annoying for me – we have to keep lazy loaded value and its value loader as separate things. In this posting I will introduce you my Lazy<T> wrapper for complex to get system parameters that uses template method to keep lazy value loader in parameter class. Problem with original implementation Here’s the sample code that shows you how Lazy<T> is usually used. This is just sample code, don’t focus on the fact that this is dummy console application. class Program {     static void Main(string[] args)     {         var temperature = new Lazy<int>(LoadMinimalTemperature);           Console.WriteLine("Minimal room temperature: " + temperature.Value);         Console.ReadLine();     }       protected static int LoadMinimalTemperature()     {         var returnValue = 0;           // Do complex stuff here           return true;     } } The problem is that our class with many lazy loaded properties will grow messy if it has all value loading code inside it. This code may be complex for more than one parameter and in this case it is better to use separate class for this parameter. Defining base class for parameters As a first step I will define base class for all lazy-loaded parameters. This class is wrapper around Lazy<T> and it also offers one template method that parameter classes have to override to provide loaded data. public abstract class LazyParameter<T> {     private Lazy<T> _lazyParam;       public LazyParameter()     {         _lazyParam = new Lazy<T>(Load);     }       protected abstract T Load();       public T Value     {         get { return _lazyParam.Value; }     } } It is also possible to extend Lazy<T> but I don’t prefer to do it as Lazy<T> has six constructors we have to take care of. Also I don’t like to expose Lazy<T> public interface to users of my parameter classes. Creating parameter class Now it’s time to create our first parameter class. Notice how few stuff we have in this class besides overridden Load() method. public class MinimalRoomTemperature : LazyParameter<int> {     protected override int Load()     {         var returnValue = 0;           // Do complex stuff here           return returnValue;     } } Using parameter class is simple. Here’s my test code. class Program {     static void Main(string[] args)     {         var parameter = new MinimalRoomTemperature();         Console.WriteLine("Minimal room temperature: " + parameter.Value);         Console.ReadLine();     } } Conclusion Lazy<T> is useful class that you usually don’t want to use outside from API-s. I like this class but I don’t like when people are using this class directly in application code. In this posting I showed you how to use Lazy<T> with wrapper class to get complex parameter loading code out from classes that use this parameter. We ended up with generic base class for parameters that you can also use as base for other similar classes (you have to find better name to base class in this case).

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  • Add class to elements which already have a class

    - by bwstud
    I have a group of divs which I'm dynamically generating when a button is clicked with the class, "brick". This gives them dimension and starting position of top: 0. I'm trying to get them to animate to the bottom of the view using a css transition with a second class assignment which gives them a bottom position: 0;. Can't figure out the syntax for adding a second class to elements with a pre-existing class. On inspection they only show the original class of, "brick". HTML <!DOCTYPE html> <html> <head> <script src="http://code.jquery.com/jquery-2.1.0.min.js"></script> <meta charset="utf-8"> <title>JS Bin</title> </head> <body> <div id="container"> <div id="button" >Click Me</div> </div> </body> </html> CSS #container { width: 100%; height: 100vh; padding: 10vmax; } #button { position: fixed; } .brick { position: relative; top: 0; height: 10vmax; width: 20vmax; background: white; margin: 0; padding: 0; transition: all 1s; } .drop { transition: all 1s; bottom 0; } The offending JS: var brickCount = function() { var count = prompt("How many boxes you lookin' for?"); for(var i=0; i < count; i++) { var newBrick = document.createElement("div"); newBrick.className="brick"; document.querySelector("#container") .appendChild(newBrick); } }; var getBricks = function(){ document.getElementByClass("brick"); }; var changeColor = function(){ getBricks.style.backgroundColor = '#'+Math.floor(Math.random()*16777215).toString(16); }; var addDrop = function() { getBricks.brick = "getBricks.brick" + " drop"; }; var multiple = function() { brickCount(); getBricks(); changeColor(); addDrop(); }; document.getElementById("button").onclick = function() {multiple();}; Thanks!

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  • PHP Changing Class Variables Outside of Class

    - by Jamie Bicknell
    Apologies for the wording on this question, I'm having difficulties explaining what I'm after, but hopefully it makes sense. Let's say I have a class, and I wish to pass a variable through one of it's methods, then I have another method which outputs this variable. That's all fine, but what I'm after is that if I update the variable which was originally passed, and do this outside the class methods, it should be reflected in the class. I've created a very basic example: class Test { private $var = ''; function setVar($input) { $this->var = $input; } function getVar() { echo 'Var = ' . $this->var . '<br />'; } } If I run $test = new Test(); $string = 'Howdy'; $test->setVar($string); $test->getVar(); I get Var = Howdy However, this is the flow I would like: $test = new Test(); $test->setVar($string); $string = 'Hello'; $test->getVar(); $string = 'Goodbye'; $test->getVar(); Expected output to be Var = Hello Var = Goodbye I don't know what the correct naming of this would be, and I've tried using references to the original variable but no luck. I've come across this in the past, with the PDO prepared statements, see Example #2 $stmt = $dbh->prepare("INSERT INTO REGISTRY (name, value) VALUES (?, ?)"); $stmt->bindParam(1, $name); $stmt->bindParam(2, $value); // insert one row $name = 'one'; $value = 1; $stmt->execute(); // insert another row with different values $name = 'two'; $value = 2; $stmt->execute(); I know I can change the variable to public and do the following, but it isn't quite the same as how the PDO class handles it, and I'm really looking to mimic that behaviour. $test = new Test(); $test->setVar($string); $test->var = 'Hello'; $test->getVar(); $test->var = 'Goodbye'; $test->getVar(); Any help, ideas, pointers, or advice would be greatly appreciated, thanks.

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  • NHibernate DuplicateMappingException when mapping abstract class and subclass

    - by stiank81
    I have an abstract class, and subclasses of this, and I want to map this to my database using NHibernate. I'm using Fluent, and read on the wiki how to do the mapping. But when I add the mapping of the subclass an NHibernate.DuplicateMappingException is thrown when it is mapping. Why? Here are my (simplified) classes: public abstract class FieldValue { public int Id { get; set; } public abstract object Value { get; set; } } public class StringFieldValue : FieldValue { public string ValueAsString { get; set; } public override object Value { get { return ValueAsString; } set { ValueAsString = (string)value; } } } And the mappings: public class FieldValueMapping : ClassMap<FieldValue> { public FieldValueMapping() { Id(m => m.Id).GeneratedBy.HiLo("1"); // DiscriminateSubClassesOnColumn("type"); } } public class StringValueMapping : SubclassMap<StringFieldValue> { public StringValueMapping() { Map(m => m.ValueAsString).Length(100); } } And the exception: NHibernate.MappingException : Could not compile the mapping document: (XmlDocument) ---- NHibernate.DuplicateMappingException : Duplicate class/entity mapping NamespacePath.StringFieldValue Any ideas?

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  • How bad is it to have two methods with the same name but different signatures in two classes?

    - by Super User
    I have a design problem related to a public interface, the names of methods, and the understanding of my API and code. I have two classes like this: class A: ... function collision(self): .... ... class B: .... function _collision(self, another_object, l, r, t, b): .... The first class has one public method named collision, and the second has one private method called _collision. The two methods differs in argument type and number. As an example let's say that _collision checks if the object is colliding with another object with certain conditions l, r, t, b (collide on the left side, right side, etc) and returns true or false. The public collision method, on the other hand, resolves all the collisions of the object with other objects. The two methods have the same name because I think it's better to avoid overloading the design with different names for methods that do almost the same thing, but in distinct contexts and classes. Is this clear enough to the reader or I should change the method's name?

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  • Seam @Factory in abstract base class?

    - by Shadowman
    I've got a series of web actions I'm implementing in Seam to perform create, read, update, etc. operations. For my read/update/delete actions, I'd like to have individual action classes that all extend an abstract base class. I'd like to put the @Factory method in the abstract base class to retrieve the item that is to be acted upon. For example, I have this as the base class: public abstract class BaseAction { @In(required=false)@Out(required=false) private MyItem item=null; public MyItem getItem(){...} public void setItem(...){...} @Factory("item") public void initItem(){...} } My subclasses would extend BaseAction, so that I don't have to repeat the logic to load the item that is to be viewed, deleted, updated, etc. However, when I start my application, Seam throws errors saying I have declared multiple @Factory's for the same object. Is there any way around this? Is there any way to provide the @Factory in the base class without encoutnering these errors?

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  • How bad it's have two methods with the same name but differents signatures in two classes?

    - by Super User
    I have a design problem relationated with the public interface, the names of methods and the understanding of my API and my code. I have two classes like this: class A: ... function collision(self): .... ... class B: .... function _collision(self, another_object, l, r, t, b): .... The first class have one public method named collision and the second have one private method called _collision. The two methods differs in arguments type and number. In the API _m method is private. For the example let's say that the _collision method checks if the object is colliding with another_ object with certain conditions l, r, t, b (for example, collide the left side, the right side, etc) and returns true or false according to the case. The collision method, on the other hand, resolves all the collisions of the object with other objects. The two methods have the same name because I think is better avoid overload the design with different names for methods who do almost the same think, but in distinct contexts and classes. This is clear enough to the reader or I should change the method's name?

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